The present invention relates generally to radiation detectors and methods. More specifically, the present invention relates to methods of selectively forming a scintillator layer on a substrate and related devices and assemblies.
Scintillation spectrometers are widely used in detection and spectroscopy of energetic photons (e.g., X-rays and γ-rays). Such detectors are commonly used, for example, in nuclear and particle physics research, medical imaging, diffraction, non destructive testing, nuclear treaty verification and safeguards, nuclear non-proliferation monitoring, and geological exploration.
A wide variety of scintillators are now available and new scintillator compositions are being developed. Among currently available scintillators, thallium-doped alkali halide scintillators have proven useful and practical in a variety of applications. One example includes thallium doped cesium iodide (CsI(Tl)), which is a highly desired material for a wide variety of medical and industrial applications due to its excellent detection properties, low cost, and easy availability. Having a high conversion efficiency, a rapid initial decay, an emission in the visible range, and cubic structure that allows fabrication into micro-columnar films (see, e.g., U.S. Pat. No. 5,171,996), CsI(Tl) has found use in radiological imaging applications. Furthermore, its high density, high atomic number, and transparency to its own light make CsI(Tl) a material of choice for x-ray and gamma ray spectroscopy, homeland security applications, and nuclear medicine applications such as intra-operative surgical probes and Single Photon Emission Computed Tomography or SPECT.
Scintillation spectrometry generally comprises a multi-step scheme. Specifically, scintillators work by converting energetic photons such as X-rays, gamma-rays, and the like, into a more easily detectable signal (e.g., visible light). Thus, incident energetic photons are stopped by the scintillator material of the device and, as a result, the scintillator produces light photons mostly in the visible light range that can be detected, e.g., by a suitably placed photodetector. Various possible scintillator detector configurations are known. In general, scintillator based detectors typically include a scintillator material optically coupled to a photodetector. In many instances, scintillator material is incorporated into a radiation detection device by first depositing the scintillator material on a suitable substrate. A suitable substrate can include a photodetector or a portion thereof, or a separate scintillator panel is fabricated by depositing scintillator on a passive substrate, which is then incorporated into a detection device.
Unfortunately, during the scintillator deposition process scintillator material can often coat areas of the photodetector or substrate other than the areas in which scintillator material deposition is specifically desired including, for example, sensitive, delicate, and/or expensive components of the photodetector or scintillator detector assembly. For example, a known manufacturing problem is that of scintillator such as CsI being deposited on the electrodes of the scintillation light detectors (photodetectors) when the scintillator layer is being formed. Common evaporation deposition processes deposit scintillator material on all exposed surfaces, including photodetector electrodes, and cleaning or pulling the scintillator material off from unwanted areas can damage the usefully deposited scintillator material and/or the electrodes that are being cleared. Thus, significant damage to the scintillator layer and/or electrical components of the photodetector substrate may be sustained in the process of removing the scintillator material from the components.
Thus, there is a need for improved techniques and methods for depositing scintillator materials on a substrate in the fabrication of scintillation detectors. In particular, methods and assemblies are needed for selectively forming a scintillator layer on a substrate, such as a photodetector, in a controlled and accurate manner, and by avoiding the damage often inflicted by current removal methods.